Research And Implementation Of Satellite Side Tone Ranging Algorithm

TT&C system is an integral part of aerospace engineering, it is an important support and guarantee system during different kinds of spacecraft’s launch, in-orbit and return stage. TT&C system has gone through the development from decentralized system to microwave unified system. According to different carrier frequency used, there are unified S-band, unified C-band and unified Ku-band. In accordance with different objects that need monitoring and controlling. TT&C system is divided into three different kinds, they are missile telemetry and control system, spaceship telemetry and control system, satellite telemetry and control system.Satellite telemetry and control system plays an important role during the satellite launching and running, as a part ranging is an important guarantee of the satellite launch and orbit determination. Side tone ranging, pseudo-code ranging and side tone plus pseudo-code mixed-ranging are three traditional ranging methods. Because of simple, mature, and high-precision side tone ranging has been widely used in unified S-band satellite telemetry and control system.This paper is based on a project, presents one way of side tone ranging. This way takes digital correlative phase detection as core, measures the phases’delay of ranging tones which are less than2k, and then calculates the main ranging tone’s unambiguous phase delay, nearly at the same time comes out the distance of the target.The modulation of microwave unified system can be divided into uplink and downlink both use PM, and uplink uses FM while downlink uses PM, in this paper we take the front one and use quadrature structure. In practical application environment because of relative motion between monitoring station and target or implementation platform’s clock drift, carrier frequency is unstable, so there comes frequency offset. This paper analyzes the influence of frequency offset to ranging results and presents a way to solve signal folding distortion. Analysis shows that when use the ranging method in this paper, frequency offset has no influence to lower side tones’phase delay, frequency offset less than1KHz has a limited influence to higher side tones’phase delay, target’s distance influenced by frequency offset is not very great too. In this paper, the main part of ranging is implemented in digital form, signal sampling frequency changes during ranging process. After a study to HB, CIC and FIR filter, author designs the multi-stage cascade interpolation and decimation structure, implements DDC and DUC at intermediate frequency. With the help of Simulink author simulates the ranging method, observes waveform and spectrum at key point, it shows that everything is consistent with theoretical expectations. This paper gives a brief introduction to the SDR platform and realizes the ranging method with Verilog. In the lab after calibration the ranging results are reasonable, which further demonstrate the feasibility of the ranging method in this paper.